Sunday, June 23, 2013

quick reduction

Still getting used to the Réduc software...

Wanted to do a quick trial of a double star measurement, the separation and position angle. Even though I had not imaged others stars for plate scale. Reviewed Michaud's notes on calibration. Double-checked at the Washington Double Star catalog for labelling (theta for separation and rho for separation).

In the interest of speed, took data from SkyTools:
  • A and B: 232°, 18.60" (as of 2003)
  • A and C: 128°, 223.40" (as of 1992)
Also checked the WDS:
  • 18002+8000STF2308AB
    • 236°, 20.7" (as of 2012)
    • 230°, 19.5" (as of 1782)
  • 18002+8000STF2308AC
    • 128°, 221.0" (as of 2004)
    • 129°, 224.8" (as of 1895)
Converted one of the better 41 Dra shots to BMP. Loaded into Réduc.

Clicked the 41 Dra A star and set as comp A. Clicked on SAO 9002 and set as comp B. Hit the AutoReduc button. Switched to Calibration mode and entered 128 for theta and 223.4 for rho.

Clicked on the A star again and set it as the first point. Then selected 41 Dra B and set it as the second point. Switched to Measure mode. And then changed to the Reduced tab.

Well, well. θ of 231.2 and ρ of 18.6. How about that.

What's unclear to me still is how, after determining the image scale from another set of stars, and the drift angle, how I would apply those numbers to an image of "unknown" quantities. It looks like I'd supply the drift angle in Δ and the scale in E, perhaps? 

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